Association between sarcopenia and clinical outcomes in patients with hepatocellular carcinoma: an updated meta-analysis

Although numerous studies have reported the association between sarcopenia and the prognosis of hepatocellular carcinoma (HCC) patients, there is lack of a newer and more comprehensive meta-analysis. Herein, a comprehensive literature search was performed on PubMed, Web of Science, the Cochrane Library, and Embase databases to identify relevant studies published up to February 2022. The outcomes were overall survival (OS), recurrence, progression‐free survival, tumor response, severe postoperative complications, and toxicity of drugs. A total of 57 studies involving 9790 HCC patients were included in the meta-analysis. The pooled prevalence of sarcopenia in HCC patients was 41.7% (95% CI 36.2–47.2%). Results demonstrated that sarcopenia was significantly associated with impaired OS (HR: 1.93, 95% CI 1.73–2.17, P < 0.001), higher risk of tumor recurrence (HR: 1.75, 95% CI 1.56–1.96, P < 0.001), lower objective response rate (OR: 0.37 95% CI 0.17–0.81, P = 0.012), and more drug-related adverse events (OR: 2.23, 95% CI 1.17–4.28, P = 0.015) in HCC patients. The subgroup analyses revealed that the OS of patients at the early stage of tumor was more severely affected by sarcopenia than for patients at other stages. Moreover, the presence of cirrhosis and Child Pugh class B increased the hazard of mortality from sarcopenia. This study has shown that sarcopenia is highly associated with poor prognosis in HCC patients. In addition, cirrhosis and poor liver functional reserve increase the danger of sarcopenia. OS was more impaired in HCC patients with sarcopenia at early stage of tumor than at other tumor stages.

www.nature.com/scientificreports/ In addition, the meta-analyses on sarcopenia and HCC published before 2019 included very few patients and studies, which limited their statistical power for subgroup analyses or clinical outcomes 17,18 . Therefore, there is need for a newer and comprehensive meta-analysis to evaluate the influence of sarcopenia on prognosis of HCC patients, with more detailed subgroup analyses, larger sample sizes, and more clinical outcomes, such as overall survival (OS), recurrence, tumor response, and adverse events. This study investigated a large number of patients and conducted subgroup analyses of different clinical outcomes, with the overarching goal of exploring the association between sarcopenia and HCC.

Methods
Search strategy. This meta-analysis was performed in accordance with the PRISMA guidelines 19 and the protocol for this meta-analysis was available in PROSPERO (CRD42022310433). A comprehensive search was performed on PubMed, Web of Science, the Cochrane Library, and Embase databases to identify relevant studies published up to February 2022. The following key words were used: "sarcopenia", "sarcopenic", "skeletal muscle", "muscle atrophy", "muscle wasting", "muscular depletion ", "HCC", "liver cancer", "liver neoplasm", and "hepatocellular carcinoma". In addition, the references of included studies were manually scanned to retrieve potentially missing studies.
Inclusion and exclusion criteria. Two independent authors (Yusheng Guo and Yanqiao Ren) conducted the preliminary review of literature identified in the databases by reading titles and abstracts. Studies were considered eligible if they met the following inclusion criteria: (1) were limited to English articles; (2) evaluated the impact of sarcopenia in HCC patients; (3) reported OS, disease-free survival (DFS), recurrence-free survival (RFS), objective response rate (ORR), disease control rate (DCR), toxicity of drugs, or postoperative complications were reported. In instances where multiple publications reported overlapping data, the study with the largest sample size was considered. Exclusion Criteria: (1) Comments, editorials, letters, case reports, reviews, and meta-analyses were not considered. (2) Duplicate documents were deleted. Data extraction. Two authors independently extracted the following data from the included studies: year of publication, name of first author, region, treatment mean, diagnostic method, cut-off value, HCC stage, outcomes, number of enrolled patients, number of patients with sarcopenia, and sex ratio. Each study was independently assessed by the two authors using the Newcastle-Ottawa scale (NOS) 20 , and studies with NOS score ≥ 6 were considered high-quality studies. Any disagreements were resolved by discussion or consensus with a third author (Lian Yang or Chuansheng Zheng).
Statistical analyses. All statistical analyses were performed using R software (version 4.1.0). Before conducting the meta-analysis, a heterogeneity test was performed using χ2 tests (α = 0.10) and the I2 metric. P < 0.05 indicated the existence of heterogeneity, and studies with I 2 > 35% were considered as having high heterogeneity. Notably, a random effects model (high heterogeneity) or a fixed effects model (low heterogeneity) was used to pool data for meta-analysis. Next, a forest map was drawn, and the HR or OR and its 95% confidence interval (CI) were described and discussed. Possible sources of heterogeneity were determined using Baujat plots and sensitivity analyses were then conducted through sequential omission of studies. Subgroup analyses of OS, recurrence, and tumor response were performed based on patients' characteristics. Finally, Egger's tests and funnel plot were performed to evaluate publication biases. Two-sided P < 0.05 were considered statistically significant for all statistical procedures.

Results
A total of 2435 studies were identified after screening the databases, from which 1867 studies were excluded, followed by reviewing the abstracts of 568 studies in accordance with the inclusion criteria. Finally, 57 studies 3,21-76 were included in this meta-analysis after detailed full-text examination (Fig. 1). Notably, sarcopenia was defined based on computed tomography (CT) or magnetic resonance imaging (MRI) in all enrolled studies. Given that two studies by Saeki et al. 46,56 had duplicated the patients, the study with more patients was included in OS and subgroup analyses 56 . Saeki et al. 46 was only used to explore the prevalence of sarcopenia. All enrolled studies were retrospective in design.
Given the high heterogeneity (I 2 = 57%), a random effects model for analysis was used to pool HR of DCR before the sensitivity analysis. Results showed that there was no significant association between DCR and sarcopenia (OR: 0.56, 95% CI 0.31-1.01, P = 0.055) (Fig. S9). In addition, the Baujat plot indicated that the study by Fujita et al. 49 contributed significantly to heterogeneity (Fig. S10). After it was excluded, the heterogeneity decreased substantially (I 2 = 14%), with the obtained result (OR: 0.46, 95% CI 0.30-0.69, P < 0.001) indicating that sarcopenia was significantly associated with worse disease control (Fig. S11).
Severe postoperative complications and toxicity of drugs. A total of four studies 24,29,31,52 reported the rate of severe postoperative complications in two groups (three studies addressed hepatectomy and one study addressed RFA). All postoperative complications were evaluated by Clavien-Dindo classification. The OR was 1.15 (95% CI 0.46-2.88, P = 0.772) and the sensitivity analyses yielded similar findings (Fig. S12, S13). After omitting the study by Levolger et al. 29 , the obtained result (OR: 0.78, 95% CI 0.36-1.67, P = 0.519) revealed that sarcopenia was not associated with the occurrences of severe postoperative complications on hepatectomy (Fig. S14).

Subgroup analyses.
Subgroup analyses of OS were conducted according to the treatments that patients underwent, BCLC stages, diagnostic methods, regions, gender, and the time points of diagnosis. With regard to the seven different treatment methods, results showed that the efficacy of most treatments (six out of the seven) could be influenced by sarcopenia (Table 1). Sarcopenia increased the risk of mortality in most patients who underwent RFA (HR: 4.46, 95% CI 2.64-7.54, P < 0.001), but it did not increase the risk of mortality in patients treated with ICIs (HR: 1.27, 95% CI 0.79-2.05, P = 0.323). It is worth noting that the earlier the BCLC stage, the higher the risk of sarcopenia. The pooled HR from three studies 56,58,68 involving 620 advanced HCC patients indicated that sarcopenia may be not associated with the OS of patients at the BCLC C stage (HR: 1.20, 95% CI 0.83-1.75, P = 0.331). In addition, subgroup analyses based on the different diagnostic methods, regions, gender, and the time points of diagnosis provided similar results.
Furthermore, we evaluated the association between the proportion of patients with different liver diseases and liver functional reserve in every cohort and OS. The results were consistent across all subgroups (Table 2) (Tables S2-S16). Specifically, it was found that the higher the proportion of patients with cirrhosis in a cohort, the more increased the risk of mortality due to sarcopenia (Tables S2-S4). Meanwhile, the lower the proportion of patients with Child-Pugh class A and the higher the proportion of patients with Child-Pugh class B, the more increased the risk of mortality (Tables S13-S16).
Subgroup analyses of ORR and DCR were conducted on patients who received systemic therapy or TACE. The detailed data of ORR and DCR were available in four studies 22,40,68,76 on systemic therapy (two studies on lenvatinib, one study on sorafenib, and one study on gemcitabine and oxaliplatin) and two studies 49,72 on TACE. Results indicated that sarcopenia was associated with lower ORR and DCR in patients that received systemic therapy instead of TACE (Table 3).

Discussion
To date, this study involving 9790 patients is the largest study that has explored the impact of sarcopenia in HCC. Although two previous systematic reviews and meta-analyses 17,18 described the negative influence of sarcopenia in HCC, they only included 13 studies and 3111 patients, which resulted in the absence of detailed subgroup analyses. The two studies also included patients with other cancers (such as intrahepatic cholangiocarcinoma), which may limit interpretation of their conclusions 77 . In this study, a more comprehensive literature search was conducted, which resulted in more HCC patients being included thereby providing more data for effective subgroup analyses. To determine and decrease the potential heterogeneity, Baujat plots and sensitivity analyses, respectively, were performed to identify the sources of heterogeneity and ensure the stability of obtained results. Results demonstrated that sarcopenia was significantly associated with impaired OS, higher risk of tumor recurrence, worse tumor response, and more drug-related adverse events in HCC patients. The calculation results showed that HCC patients with sarcopenia had a 1.93 times higher risk of death, 1.75 times higher risk of recurrence, 0.37 times lower odds of tumor response, and 2.23 times higher odds of adverse drug reactions than HCC patients without sarcopenia. Despite the existence of heterogeneity in the OS data analysis, the sensitivity analyses and the consistency of results derived from different subgroups further validated our results.
In the subgroup analyses, we did not divide the treatment means into curative therapy or palliative treatment like previous meta-analysis 17 because many studies using curative therapy included patients at the BCLC B or C stage who were beyond the indications of curative therapy 4,24,29,31 . Therefore, the subgroups were clearly divided according to specific therapies and BCLC stages. It was found that patients with sarcopenia at early stage were more vulnerable, and thus we speculated that other risk factors such as tumor metastasis or tumor thrombus were the more important factors leading to death in the patients at more advanced stages. However, the skeletal muscle mass representing systemic nutritional states was associated with the tolerance of operation on the liver like RFA, hepatectomy or LDLT. Meanwhile, HCC patients with sarcopenia suffered higher rates of liver failure, major complications, and intra-abdominal abscess formation 78,79 . Ultimately, OS was significantly impaired in patients with sarcopenia at early stage. In addition, frailty has a very close overlap with sarcopenia 80 . Frailty was associated with an increased risk for mortality and morbidity related to cancer and worse response to treatment 81 , therefore, this could result in decreased numbers of frail patients who received TACE, hepatectomy, or systemic treatment. This selection bias could explain why we found more impact of sarcopenia in the BCLC-0/BCLC-A groups in comparison with those treated with TACE or systemic treatment. Moreover, it could also explain why sarcopenia was not associated with complications after hepatectomy (Fig. S14).
A previous study reported that chronic underlying liver diseases contributed to the process of hepatocarcinogenesis 82 . Moreover, a recent meta-analysis revealed that sarcopenia was highly associated with higher risk of mortality in patients with cirrhosis 6 . Similarly, this study found that HCC patients with more proportion of cirrhosis were at a higher risk of mortality, suggesting the synergistic effect of cirrhosis and HCC. Therefore, more emphasis should be given for the influence of sarcopenia in HCC patients with cirrhosis. In addition, we found that the proportion of patients with different Child-Pugh classes may affect the association between sarcopenia and OS. Table 1. Subgroup analyses of overall survival. ICIs immune checkpoint inhibitors, RFA radiofrequency ablation, TACE transarterial chemoembolization, TARE transarterial radioembolization, BCLC Barcelona Clinic Liver Cancer, SMI skeletal muscle index, PMI psoas muscle index. *Delta: sarcopenia was defined with the change of skeleton muscle during or after the treatment.

Subgroup
No. of studies No. of patients Estimates (HR) Lower limit to Upper limit P-value www.nature.com/scientificreports/ Given the impact of sarcopenia on HCC, more attention should be paid on the prevention of sarcopenia and rehabilitation treatment in HCC patients with sarcopenia. Nutritional support and physical exercise are two promising strategies that can improve the skeletal muscle state and long-term prognosis 78 . A previous retrospective study reported that L-carnitine improved sarcopenia progression in HCC patients treated with lenvatinib, and patients with L-carnitine supplementation tended to have a longer median time to treatment failure compared to patients without L-carnitine supplementation 83 . A study conducted in Japan found that in-hospital exercise may prevent sarcopenia in HCC patients who underwent TACE 84 , which suggested the necessity and feasibility of sarcopenia prevention.
However, this meta-analysis had several limitations. First, all the included studies are retrospective studies, which leads to inevitable selection bias and confounding bias. Second, it was hard to compare differences between the hazard of sarcopenia occurring in the course of treatment and the hazard of baseline sarcopenia because only three studies on the change of skeleton muscle mass during or after the treatment were included in the subgroup analyses. Similarly, only two studies explored the association between sarcopenia and prognosis in patients who underwent immunotherapy, thus, it was hard to draw conclusions on the effect of sarcopenia on the efficacy of ICIs. Third, most studies involved patients with different etiologies of chronic liver diseases and Child Pugh classes, thus, it was hard to directly evaluate the impact of chronic liver diseases and liver functional

Conclusion
This meta-analysis demonstrated that sarcopenia was associated with significantly impaired OS, higher risk of tumor recurrence, worse tumor response, and more drug-related adverse events in HCC patients. The presence of cirrhosis and Child Pugh class B increased the hazard of mortality from sarcopenia. HCC patients at early stage of tumor had more impaired OS resulting from sarcopenia than other tumor stages.

Data availability
The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.